The present invention relates to the field of archery, more specifically to hunting arrowheads called broadheads. There are two types of broadheads: fixed where there are no moving parts and a constant cutting diameter, and mechanical where there are moving parts. Mechanical broadheads have less surface area in flight for great accuracy, and an expanding diameter when contacting the animal for greater cutting diameter than when passing the bow riser and in flight.
A common problem of mechanical broadheads with the tips of the sharpened blade edges near the tip of the ferrule or head body is that the force it takes to open the blades reduces penetration, such as in Mizek et al., U.S. Pat. No. 5,564,713. Also, when a bone is hit upon entry the blade tip may act in a “pole vaulting” manner and push the arrow out from its intended path to a different angle and cause a non-fatal hit.
Another disadvantage is a small entry wound, such as is produced by the head described in Johnson, U.S. Pat. No. 5,879,252 where the blade tips enter the animal without having a fully expanded diameter. With a small entry hole, blood will not exit well for tracking. Also long slender blades have proven fragile when contacting bone.
Barrie et al., U.S. Pat. No. 6,910,979 attempts to improve mechanical performance by having the blades slide rearward, eliminating the pole vaulting effect of the blade tips. However, as in some other designs, blade securement is a problem, as the blade tips are lightly secured inserted inside an O-ring, such that removing the arrow from the quiver or the shock of launch may cause the head to open prematurely during flight, planing it off course. Further, the head is barbed in both its open and, more importantly, closed positions.
Forrest et al., U.S. Pat. No. 5,458,341, uses a trip blade to open the main cutting blade after that blade has penetrated the animal. This again produces a small entry wound. Also if the trip blade hits bone, it prevents the main blades from opening so the arrowhead loses penetration energy and is deflected.
Other patents on similar systems with similar problems include Vance, U.S. Pat. No. 2,820,634; Carlston, et al., U.S. Pat. No. 5,078,407; Ward, U.S. Pat. No. 5,286,035; Barrie et al., U.S. Pat. No. 6,517,454; Barrie et al., U.S. Pat. No. 6,910,979; Wohlfeil et al., U.S. Pat. No. 7,377,869; and Ward, U.S. Pat. No. D583,897.
All of the foregoing patents are hereby incorporated by reference.